1. Field of the Invention
The present invention relates to a black oxonol pigment, to a black pigment dispersion comprising the black oxonol pigment, and to a black resin composition comprising the black oxonol pigment. More particularly, the present invention relates to a black oxonol pigment with little absorption in the near infrared range, to a black pigment dispersion comprising the black oxonol pigment, and to a black resin composition comprising the black oxonol pigment.
2. Discussion of the Background
Conventionally, carbon black, aniline black, iron oxides and the like have been employed as black pigments. These pigments absorb light over a wide range spanning from the ultraviolet range to the far infrared range. In contrast, some semiconductor lasers, and sensors employing such lasers, use light in the near infrared range. There is a problem in that conventional black pigments cannot be differentiated from near infrared absorbing pigments by such sensors. When paint or plastic materials comprising conventional black pigments are employed on automobiles or buildings, there are problems in that the internal temperature rises, cooling efficiency decreases, and surfaces are denatured by heat.
To solve these problems, various pigments have been proposed as black pigments that do not absorb light in the near infrared range. As such pigments, azo pigments are described, for example, in Japanese Unexamined Patent Publication (KOKAI) Heisei No. 11-236,514, and Japanese Unexamined Patent Publication (KOKAI) No. 2002-256,165 or English language family member U.S. Patent Application Publication No. 2002/0121228 A1, which are expressly incorporated herein by reference in their entirety, and pigments such as perilene, diketopyrrolopyrrole, quinophthalone, perinone, dioxazine, phthalocyanine, isoindoline, and isoindolinone are described, for example, in Japanese Unexamined Patent Publication (KOKAI) No. 2002-20,647, Japanese Unexamined Patent Publication (KOKAI) No. 2002-60,698 or English language family member U.S. Patent Application Publication No. 2003/0030041 A1, and Japanese Unexamined Patent Publication (KOKAI) No. 2005-132,461, which are expressly incorporated herein by reference in their entirety. However, further improvement in hue, that is, increased blackness and better transparency in the near infrared range, is desirable in these pigments. Further, better pigment processing (comminution) properties and ease of pigment dispersion are also desirable.